Presbyopia is a condition where the eye exhibits a progressively diminished ability to focus on near objects due to a loss of elasticity of the crystalline lens. Apart from the application of corrective lenses, conventional treatment may also involve surgery. In such surgery, the first step is to make a corneal incision to form an opening to the anterior lens capsule with a process called capsulorhexis. After this the entire lens is removed, typically involving the emulsification of the lens using ultrasound, and then a synthetic intra-ocular lens (IOL) is inserted.
An alternative treatment is called the phaco-ersatz technique. The procedure involves the removal of the cortex and nucleus while preserving the lens capsule and its zonular attachments. The empty lens capsule is then refilled with biocompatible and optically suitable clear gel. The phaco-ersatz technique involves the removal of as much of the lens core and lens epithelial cells (LEC) as possible with the aim of (1) maximising accommodative outcome; and (2) eliminating LEC, the source of posterior capsular opacification (PCO) which is an adverse effect associated with intracapsular surgery including cataract with IOL implantation. PCO can degrade vision to the point when ophthalmic surgical intervention is required. Aspirators and phaco-emulsification probes (or “phaco-probe”) are used to remove the entirety of the lens core and LEC.
A number of advances have been made in the phaco-ersatz technique. For example, in one improved technique the hardened core (cortex and nucleus) of a presbyopic lens is first removed using a procedure modified from the extracapsular cataract extraction (ECCE) procedure; the main modification being the evacuation of lens material via a peripheral, mini-capsulorhexis. The patency of the capsule is maintained during this procedure. Following extraction of the lens core, a synthetic material, usually a polymer gel with the appropriate physical (mechanical and optical) properties, is used to refill the capsule via the mini-capsulorhexis.
Further enhancements include the use of improved polymer gels for restoring accommodation in presbyopes, as well as the use of a valve for sealing the capsulorhexis (or capsulotomy).
Despite advances made in the available polymer gels and the procedure, there are still some challenges to achieving a clinically acceptable end-product, for example:                Despite the removal of almost all LEC in the procedure, PCO (the unregulated proliferation of LEC causing severe loss of visual quality) continues to be a problem to medium/long-term success.        In order to eliminate as much LEC as possible, in a conventional cataract operation, an irrigation and aspiration (I/A) probe is used to remove the lens cortex and the tip of the I/A probe will be in direct contact with the capsule when removing the LEC from the anterior part of the capsule. The risk of capsule rupture is substantial. Rupture can be caused by the inadvertent application of direct suction on the internal capsule surface due to an accidental misplacement of the aspirator or phaco-probe tip. A rupture of the capsule renders the lens ineligible for phaco-ersatz with a polymer gel and a more conventional treatment (e.g. IOL) is required. The patient thereafter cannot enjoy the benefits of high amplitude, continuous focus accommodation made possible by lens refilling.        The physical property of the polymer gel is such that it is difficult to fill the capsule to the lens equator. Typically, a ‘void’ remains which (1) presents a site for LEC proliferation and PCO; (2) reduces mechanical coupling between the intracapsular gel and the equatorial lens capsule which reduces the efficiency and efficacy of mechanical accommodation.        For some versions of the polymer gel, irradiation directed through the dilated pupil is required to cure (photo-crosslink) the gel. Since the iris overhangs the lens regardless of levels of mydriasis, gel lying at the peripheral, near-equatorial regions of the lens often does not receive sufficient radiation and becomes under-cured or remains uncured. This presents a greater risk for post-operative leakage of gel into the eye, increasing the potential for ophthalmitis and other complications.        In addition to suffering from presbyopia, a person may also be experiencing refractive error. For example, a presbyope may also be a myope (individual short-sightedness) or a hyperope (individual with long-sightedness) or an astigmat (individual with astigmatism).        